A．The departing ships seemed to be smaller and smaller when they sailed away.
B．The greater a concentration of mass is at the poles, the stronger its gravitational pull.
C．The length from Earth’’s center to sea level at the equator is longer than that at the poles.
D．The changes in the rising of a few millimeters on Earth’’s surface detected by modern devices.

A．Owing to many dynamic factors, the earth’’s shape changes.
B．Owing to the passage of time, the earth’’s shape changes.
C．Owing to being not a perfect oblate sphere, the earth’’s shape changes.
D．Owing to ocean tides, the earth’’s shape changes.